Performance and Power Consumption Management Functions in Intel Pentium 4 and Intel Xeon. Part 2: New Processors, New Technologies

Automatic thermal monitoring mechanism #2

Attentive readers may have noticed: the Thermal Monitor 2 technology was already reviewed in the previous article, why review it again here? The answer to this question will be simple and unexpected – after the tests we found out that in fact the reviewed model of Xeon Nocona (D0 stepping, CPUID signature – 0F34h) did not support TM2! To be more exact: "TM2 is enabled, but NOT supported". It is really enabled – this technology is indicated in CPUID Feature Flags. And according to the test results, it works fine. But at the same time it's "not supported"... So we decided to examine this technology using a processor (not a production sample, though), which supports it officially.

The research technique will be absolutely the same: 100% load applied to both logical processors and a stopped fan in the CPU cooler.

The result is quite expectable (and the picture is similar to the one we obtained with a Xeon processor) – when a processor reaches 73°C, the effective CPU clock decreases together with CPU load. The FID/VID graph demonstrates FID fluctuations between the two levels – minimum and maximum. At the same time you can see that VID can be switched via intermediate states (as in C1E, only the changes are more abrupt).

TM2 starts to work at its full in about a minute after the fan is stopped. The effective CPU clock reaches 2.8 GHz, the CPU load stops at 77.7%, and FID/VID stop at the level of target values (TM2 Target FID/VID) 14x and 1.2V correspondingly.

Active CPU cooling restoration results in the same changes mentioned above,
just in the reverse order.

To get a complete picture, we ran a third party utility ThrottleWatch and repeated this test (when it was released, we already had no opportunity to test its operation in TM2 mode). The result is obvious – ThrottleWatch can detect and track the moment when the system enters/leaves TM2. However, its functionality in other CPU throttling modes is still dubious.